1. Technical Field
The present invention relates to projection type display apparatuses equipped with a plurality of liquid crystal panels and optical units.
2. Related Art
In a projection type display apparatus including a plurality of liquid crystal panels as light valves, a beam of light emitted from a light source is modulated by the plurality of liquid crystal panels, thereafter the modulated beams of light are combined and projected onto a projection target such as a screen by a projection optical system. A red-color liquid crystal panel to which a beam of red light is supplied, a green-color liquid crystal panel to which a beam of green light is supplied and a blue-color liquid crystal panel to which a beam of blue light is supplied are frequently used as the liquid crystal panels. In such projection type display apparatus, since a beam of light having a shorter wavelength is supplied to the blue-color liquid crystal panel in comparison with the other crystal panels, its crystal layer is likely to be deteriorated.
Regarding a blue-color liquid crystal panel, there has been proposed a technique that lengthens the lifetime of a blue-color crystal panel by making the structure of the blue-color crystal panel differ from the structures of the other crystal panels (green-color and red-color liquid crystal panels) (see JP-A-2009-31545). In JP-A-2009-31545, it is proposed to make the size of a blue-color liquid crystal panel larger than the size of the other liquid crystal panels (green-color and red-color liquid crystal panels), for example.
However, in the case where the size of the blue-color liquid crystal panel is made larger than the size of the other liquid crystal panels (green-color and red-color liquid crystal panels) as in a configuration example described in JP-A-2009-31545, there arises an unfavorable problem in that requirements to largely change the design of a first substrate and a second substrate, manufacturing process and the like must be satisfied.
Hereinafter in this application, the inventors of the invention propose a technique that enhances light resistance of a blue-color liquid crystal panel by improving the ultraviolet absorption spectrum of a material itself used in the liquid crystal layer of the blue-color liquid crystal panel. With the configuration in the proposal, an advantage is achieved such that the design of the first and the second substrates, manufacturing process and the like are not required to be changed.
In JP-A-2009-31545, it is proposed to lower the concentration of a terphenyl derivative in the liquid crystal layer of the blue-color liquid crystal panel in comparison with the other liquid crystal panels (green-color and red-color liquid crystal panels). However, such configuration is intended to reduce the content of the terphenyl derivative, which causes decrease in light resistance, in the blue-color liquid crystal panel, and is different from the configuration proposed by the inventor in this application by which the ultraviolet absorption spectrum is improved. Further in JP-A-2009-31545, it is proposed to add an ultraviolet absorbing agent to the liquid crystal layer of the blue-color liquid crystal panel and not to add an ultraviolet absorbing agent to the liquid crystal layers of the other liquid crystal panels (green-color and red-color liquid crystal panels). However, even if the ultraviolet absorbing agent is added, it is difficult to sufficiently enhance the light resistance of the blue-color liquid crystal panel because it is difficult for the liquid crystal layer to avoid the receiving of a beam of light before the ultraviolet absorbing agent absorbs the beam of light. Furthermore, the ultraviolet absorbing agent can possibly change an orientation characteristic and the like of the liquid crystal layer.